Hi everyone! My name is Sierra Melton and this fall I will be a sophomore at Colorado College in Colorado Springs, where I am studying geology and environmental science. This summer I am excited to be working with Dr. Jim McClelland and Dr. Amber Hardison. We are investigating nitrogen cycling in the tidally-influenced freshwater zones (termed oscillic zones) of the Mission and Aransas rivers. Anthropogenic influences such as runoff from artificial fertilizers and sewage can increase the concentration of nitrogen in rivers. The oscillic zone and its ability to remove nitrogen are therefore important because an increase in nitrogen, often the limiting nutrient in algal growth, can result in harmful algal blooms. I will be assisting Amber and Jim with their research on the role of oscillic systems in transforming and removing nitrogen before it enters the estuary. We will collect sediment cores in order to measure gas (oxygen, nitrogen) and nutrient (ammonium, nitrate, nitrite) fluxes between the sediment and water. Additionally, I will be studying some geochemical properties of the sediment that could impact nitrogen cycling. I will analyze sediments to determine grain size, porosity, and organic matter content (percents of carbon and nitrogen). Then I will compare these data between rivers as well as between sediment depths and sampling locations within a river. Since the sediment is an important zone of nitrogen transformation, information from my analysis will help Jim and Amber interpret their data.